Method for the production of cored patterns



May 16, 1967 N. G. LlRONES I 3,320,345

METHOD FOR THE PRODUCTION OF BORED PATTERNS FIG. 2

/ fi ag I azz' s- May 16, 1967 N. G. LIRONES METHOD FOR THE PRODUCTIONOF CORED PATTERNS 2 Sheets-Sheet 2 Original Filed Jan. 27, 1961INVAENTOR. 722.026 G [1 rones United States Patent 3,320,345 METHOD FORTHE PRODUCTION OF CORED PATTERNS Nici: G. Lirones, North Muskegon,Mich., assignor, by

mesne assignments, to Howmet Corporation, a corporation of DelawareContinuation of application Ser. No. 85,322, Jan. 27, 1961.

This application Feb. 15, 1965, Ser. No. 432,686 Claims. (Cl. 264-255)This invention relates to an apparatus and method for the production ofcored patterns and, more particularly, it relates to the preparation ofcored patterns having extremely small cores positioned Within thepatterns.

This application is a continuation of my copending application Ser. No.85,322, filed Jan. 27, 1961, and entitled: Apparatus and Method for theProduction of Cored Patterns.

The present invention finds particular application in the production ofturbine blades and like components provided in engines developing highspeed and power. In order for such engines to realize maximumefiiciency, it is required that the turbine vanes and like parts becapable of withstanding high temperatures. In addition to providing newalloys and novel designs of such parts for withstanding such hightemperatures while still maintaining adequate strength, it has beenproposed that passages be provided in such components through which acoolant, such as air, may be circulated during engine operation. Theprovision of such passages has been proven extremely difficult andcostly in that machining has been impractical because of the length andsmall dimension of the passages coupled with the character of the metaland also because straight passages were seldom permissible, due to thedesign of the blades. Conventional casting processes have been found tobe inadequate to handle the delicate cores required.

The portions of the blades through which the cooling passages are toformed are extremely thin, and it is therefore necessary that the coresmust be positioned with extreme precision. Since the passages arenecessarily extremely small, the cores are very delicate and it has beendiflicult to maintain the position of the cores during pattern making.

It is an additional object of this invention to provide a method for thepositioning of extremely small cores within thin patterns with extremeprecision.

It is an additional object of this invention to provide a method whichpermits the achieving of the foregoing object when the cores arecomposed of glass or ceramic materials and are to be positioned withinexeremely thin wax patterns.

These and other objects of this invention will appear hereinafter andfor purposes of illustration, but not of limitation, specificembodiments of this invention are shown in the accompanying drawings, inwhich FIGURE 1 is a sectional view of two of the mold sections employedin the process of this invention shown in spaced-apart fashion;

FIGURE 2 is a sectional view of the mold sections of FIGURE 1 shownfilled with pattern material;

FIGURE 3 is a sectional view of the mold sections of FIGURE 1 shown inspaced-apart fashion after formation of the pattern;

FIGURE 4 is a top plan view of the lower mold section shown in FIGURE 3,with the core elements inserted therein;

FIGURE 5 is a sectional view of the pattermmaking apparatus of thisinvention, including the second upper mold section associated with thelower mold section of the previous figures; and

FIGURE 6 is a perspective view of the completed pattern with coreelements therein in accordance with this invention.

The present invention may be broadly described as a procedure wherein afirst die having a cavity corresponding to one portion of a pattern isassociated with a second die and this pattern portion formed. The firstpattern portion formed will be provided with grooves for the insertionof the desired core elements in their desired positions. A third diemember is then provided having a cavity corresponding to the remainingportion of the pattern and the pattern material is injected, thusproviding a completed pattern.

This invention will be more readily understood when considering theaccompanying drawings wherein FIG- URES 1-3 illustrate first and seconddie halves 10 and 12 adapted for carrying out the initial steps of theinventive shown provided with a molding contour 14 corresponding to theunder surface 16 of the completed pattern element 18 (FIGURE 6). Thesecond die half 12 has a molding contour 20 corresponding to a surfacewhich approximately bisects the core positions desired in the ultimatepattern element. The surface may be defined as that surface formed by aninfinite number of lines drawn from an edge of the element 18approximately through the center of the core positions therein to anopposite edge. The surface, and accordingly the molding contour 20, ofthe die half 12 will thus depend on the desired core positions in thepattern element.

The die half 12 is provided with obtrusions 21 which are dimensioned toform grooves 23 in the pattern portion 30 formed by the die halves 10and 12. The obtrusions 21 and the grooves 23 formed thereby willcorrespond to approximately one-half the core dimensions to be employed.

The third die half 22 (FIGURE 5) has a molding contour 24 correspondingto the upper surface 26 of the element 18.

Core elements 28 are adapted to be fitted within the recesses 23 formedin a pattern portion 30 by the obtrusions 21. The core elements 28 arepreferably formed of hollow glass or ceramic elements whereby they maybe removed from the vane ultimately formed therefrom, for example, bythe passage of hydrofluoric acid through the hollow spaces in the cores.

It will be noted in FIGURE 4 that the die half 10 has extensions 29formed therein which provide a resting point for the core elements 28.As can be seen, these extensions 29 correspond directly with therecesses 23.

The operation of this invention may be best understood when consideringthe following preferred embodiment. In the manufacture of wax patternsfor the production of turbine vanes, such as the patterns shown inFIGURE 6, the die halves 12 and 10 are placed in operative position. Waxis then injected, and there results a pattern portion 30 with therecesses 23 therein. The parting compound which is conventionallyemployed in pattern making will then be removed from the surface 32 ofthe pattern portion 30, for example, by swabbing this surface withtrichloroethylene. The hollow glass cores 28 may then be inserted in therecesses 23, the die half 22 brought into operative engagement as shownin FIGURE 5, the wax injected for the formation of the completedpattern.

In many instances it has been found unnecessary to provide the recesses23 throughout the entire length of the pattern portion 30. It has beenfound desirable to provide intermediate areas where wax injected intothe die halves and 22 will entirely surround the elements 28. Forexample, the die half 12 would be provided with a projection beyond theabove-defined contour 20, thus extending beyond the surfacecorresponding thereto. Therefore, when the die halves 10 and 12 aremated, the recesses 23 will be interrupted by the cavity formed in thepattern portion 30 by the said projection. The cores 28, which areplaced in the recesses, will bridge the cavity, and Wax injected whenthe die halves 10 and 22 are mated will completely surround the cores28.

This above-described construction is advantageously employed where thecores are not straight and it would be improvident to providecorresponding obtrusions 21 in the die half 12. Furthermore, theconstruction is desirable since it assures the accurate locking of thecore elements in the desired positions when wax from the first injectioncompletely surrounds the elements 28. It is, of course, required thatthe bridging eifect by the formation of the intermediate cavities shouldnot be such that the core elements fracture when wax is injected underpressure.

The principles of this invention are adapted for use in all similartypes of pattern manufacture where problems similar to the above mayarise. The pattern and core materials and the particular patternelements set forth in the specific examples, described above, are not tobe considered limiting but exemplary only.

It will be apparent from FIGURE 6 that the ends of the cores 28 extendbeyond the injected pattern portion so as to be available to becomeembedded in the ceramic walls of the shell mold that are built up aboutthe pattern as in the shell molding process described in the OperhallPatent No. 2,961,751 or in convention shell molding or investmentcasting processes. Thus the cores will be supported at their ends to beretained in place within the mold cavity of the shell mold after theinjected portion of the pattern has been removed.

It will be understood that the first pattern portion that is formed withthe grooves for receipt of core members may constitute an intermediateportion of the pattern having grooves on opposite sides for positioningthe described cores and wherein the first die members constitute dieparts to define the completed pattern whereby pattern material can beinjected therein to complete the pattern with the core members embodiedin position of use.

It will be understood that various modifications may be made in theaboveaiescribed process and apparatus for the production of coreelements which provide the characteristics of this invention withoutdeparting from the spirit of this invention, particularly as defined inthe following claims.

I claim:

1. In a method for the production of metal castings having elongatepassages of small dimension extending internally therethrough by thebuild-up of a mold having walls about a pattern formed of disposablematerial and disposing of the pattern to leave a corresponding moldcavity within the walls of the mold, the process of producing thepattern having cores extending therethrough in the areas correspondingto the passages comprising providing first and second die parts defininga portion of the mold pattern in a cavity therebetween with at least oneof said die parts having at least one obtrusion in the face thereofcorresponding to the extent that said pattern portion will be occupiedby said cores and in which the obtrusions extend to an edge of saidpattern, and continue across the adjacent edges of the one die part toconform with corresponding recesses in another die part, closing saiddie parts, introducing the pattern material into the cavity to form saidpattern portion with impressions being formed in the surfaces of saidpattern portion due to the presence of said obtrusions, opening said dieparts, providing core members having a length greater than the length ofsaid impressions, placing said core members in the impressions formed bysaid obtrusions whereby the ends of said core members extend beyond theopposite ends of the impressions and beyond said adjacent adges of thedie part, providing other die parts defining a cavity therebetwcencorresponding to the completed pattern, mating said die parts with theformed pattern portion in the desired position within the cavity,introducing pattern material into the cavity to complete the patternwith the cores embedded therein and with the ends of the cores extendingbeyond the completed pattern.

2. The method as claimed in claim 1 which includes the steps of applyinga parting compound to the surfaces of the first and second die parts,and applying solvent to the exposed surfaces of the formed patternportion to remove the parting compound before positioning said patternportion within the other die parts to form the completed pattern.

3. The method as claimed in claim 1 in which the cores are of a ceramicmaterial and in which the pattern is formed of a heat disposablematerial.

4. The method as claimed in claim 1 in which the other die parts areformed with grooves aligned with the impressions in the pattern portiondisposed therebetween for receipt of the ends of the core members whichextend beyond the pattern portion.

5. The method as claimed in claim 1 in which the first and second dieparts have obtrusions in each of their surfaces whereby impressions toreceive the cores are formed in both of the opposite surfaces of thepattern portion.

References Cited by the Examiner UNITED STATES PATENTS 665,989 1/1901Bechtold 264157 771,594 10/1904 Wilhelmi 264279 1,625,449 4/1927 Bohn etal. 264275 1,827,549 10/1931 Villain 264275 2,887,744 5/1959 Halliday22158 2,921,352 1/1960 Pfeifie 22-158 3,120,573 2/ 1964 Ging-rande et'al 264277 3,136,833 6/1964 Wikkerink 264277 ROBERT F. WHITE, PrimaryExaminer.

F. MARLOW, L. S. SQUIRES, R. B. MOFFITT,

Assistant Examiners.

1. IN A METHOD FOR THE PRODUCTION OF METAL CASTINGS HAVING ELONGATEPASSAGES OF SAMLL DIMENSION EXTENDING INTERNALLY THERETHROUGH BY THEBUILD-UP OF A MOLD HAVING WALLS ABOUT A PATTERN FORMED OF DISPOSABLEMATERIAL AND DISPOSING OF THE PATTERN TO LEAVE A CORRESPONDING MOLDCAVITY WITHIN THE WALLS OF THE MOLD, THE PROCESS OF PRODUCING THEPATTERN HAVING CORES EXTENDING THERETHROUGH IN THE AREAS CORRESPONDINGTO THE PASSAGES COMPRISING PROVIDING FIRST AND SECOND DIE PARTS DEFININGA PORTION OF THE MOLD PATTERN IN A CAVITY THEREBETWEEN WITH AT LEAST ONEOF SAID DIE PARTS HAVING AT LEAST ONE OBTRUSION IN THE FACE THEREOFCORRESPONDING TO THE EXTENT THAT SAID PATTERN PORTION WILL BE OCCUPIEDBY SAID CORES AND IN WHICH THE OBTRUSIONS EXTEND TO AN EDGE OF SAIDPATTERN, AND CONTINUE ACROSS THE ADJACENT EDGES OF THE ONE DIE PART TOCONFORM WITH CORRESPONDING RECESSES IN ANOTHER DIE PART, CLOSING SAIDDIE PARTS, INTRODUCING THE PATTERN MATERIAL INTO THE CAVITY TO FORM SAIDPATTERN PORTION WITH IMPRESSIONS BEING FORMED IN THE SURFACES OF SAIDPATTERN PORTION DUE TO THE PRESENCE OF SAID OBTRUSIONS, OPENING SAID DIEPARTS, PROVIDING CORE MEMBERS HAVING A LENGTH GREATER THAN THE LENGTH OFSAID IMPRESSIONS, PLACING SAID CORE MEMBERS IN THE IMPRESSIONS FORMED BYSAID OBTRUSIONS WHEREBY THE ENDS OF SAID CORE MEMBERS EXTEND BEYOND THEOPPOSITE ENDS OF THE IMPRESSIONS AND BEYOND SAID ADJACENT EDGES OF THEDIE PART, PROVIDING OTHER DIE PARTS DEFINING A CAVITY THEREBETWEENCORRESPONDING TO THE COMPLETED PATTERN, MATING SAID DIE PARTS WITH THEFORMED PATTERN PORTION IN THE DESIRED POSITION WITHIN THE CAVITY,INTRODUCING PATTERN MATERIAL INTO THE CAVITY TO COMPLATE THE PATTERNWITH THE CORES EMBEDDED THEREIN AND WITH THE ENDS OF THE CORES EXTENDINGBEYOND THE COMPLETED PATTERN.